What to do if i was pregnant with a baby who had this disease and it led to heart failure before he was born. anybody know anything about it?

Pregnancy induced: It is called pregnancy induced cardiomyopathy. If somebody has it, you don't need worry unless until you get it. There is no way to prevent it. If it happens we can treat it.

Hydrops: It sounds like you are describing a condition called hydrous fetalis which is "heart failure" in a baby before it is born. There are many potential causes including congenital infections, severe fetal anemia due to either infection or maternal fetal blood type incompatibility, low heart rate or very fast heart rate, or other causes. These problems may or may not recur in future pregnancies.